Browsing by Author "Wanga, Lucy Aketch"

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Determination of antibacterial activity of extracts from markhamia lutea, zanthoxylum gilletii and their endophytes against common bean bacterial pathogens
(Egerton University, 2018-09) Wanga, Lucy Aketch
Common bean (Phaseolus vulgaris L.) is largely consumed among various communities in Kenya. However, its productivity is gradually declining due to infections such as common bacterial blight and halo blight. Zanthoxylum gilletii and Markhamia lutea have been used traditionally in the management of various human bacterial pathogens. In addition, plants are inhabited by fungal endophytes that produce bioactive secondary metabolites. This study therefore, was to determine the bioactivity of secondary metabolites from Z. gilletii, M. lutea and their fungal endophytes against Xanthomonas axonopodis pv. phaseoli and Pseudomonas syringae pv. phaseolicola, the causal agents of bean common bacterial blight and halo blight. The fungal endophytes were isolated from sterilized leaves, plated on Sabourand Dextrose Agar (SDA) media amended with streptomycin sulphate, incubated and subcultured. A total of 51 fungal endophytes were isolated and 50% identified. Fifteen (15) endophytes were active against the test organisms with Fusarium solani producing the best activity in the dual culture assay. The most active endophytes were fermented on rice media and extracted using methanol by ultrasonification. Methanol extract was partitioned between ethyl acetate and hexane to produce ethyl acetate and hexane extracts respectively. Purification of the ethylacetate extract produced 2-hydroxyphenylacetic acid (14), 4-hydroxyphenylacetic acid (13) and (E)-3,8-dimethyl-7-(4-methylhex-2-en-2-yl)- 7,8-dihydro-5Hpyrano[4,3-b]pyridine-2,4,8-triol(Lucinine)(15). Secondary metabolites from the dried leaves were extracted using methanol. Methanol extract was fractionated using methanol, ethyl acetate and hexane to obtain Skimmianine (5) from the methanol extract of Z. gilletii. The pure compounds were analyzed by a combination of mass spectrometry and spectroscopic techniques which included 1D and 2D NMR. All the extracts except methanol crude extract from Z. gilletii were active against X. axonopodis pv. phaseoli while only the Fusarium extracts were active against P. syringae pv. phaseolicola, in the disc agar diffusion assay. Qualitative and quantitative violacein assay were used to assess quorum quenching properties of these extracts. Fusarium solani extracts and Z. gilletii ethyl acetate extract showed a potential activity in the qualitative (overlays) and quantitative violacein assay. These results demonstrate the diversity of endophytic fungal genera inhabiting the two medicinal plants and the potential of these plants and their endophytic fungal extracts as sources of antibacterial and quorum quenching secondary metabolites. This study also provides leads for the control of the bacterial pathogens affecting common bean in Kenya
Evaluation of antimicrobial, antidermatophytic, antiproliferative and cytotoxic activity of secondary metabolites isolated from calpurnia aurea subsp. aurea (aiton) benth (l’herit) and associated fungal endophytes
(Egerton University, 2025-09) Wanga, Lucy Aketch
Antimicrobial resistance has been recognized as a significant threat to healthcare systems globally, affecting both developing and developed countries, resulting in increased rates of skin infections caused by bacterial and dermatophytic pathogens. Cancer cases have increased over the years, and existing management options often entail undesirable side effects. Medicinal plants and endophytic fungi provide alternative solutions to these challenges. This research focused on the isolation of antimicrobial, antidermatophytic, antiproliferative, and cytotoxic secondary metabolites from Calpurnia aurea subsp. aurea and its associated endophytic fungi. The leaves and stem bark of this medicinal plant were used for the isolation of endophytic fungi, while the remaining portions were used for secondary metabolite extraction using methanol. Isolated fungal endophytes were identified through molecular techniques and fermented on rice media for the extraction of secondary metabolites. All extracts from leaves, stem bark, and endophytic fungi were purified using High Performance Liquid Chromatography (HPLC) to isolate pure compounds. The structures of the isolated compounds were elucidated using 1D and 2D NMR spectroscopy, as well as Liquid Chromatography Mass Spectrometry techniques. The bioactivities (antimicrobial, antidermatophytic, antiproliferative, and cytotoxicity) of the isolated compounds were also analyzed. Nineteen endophytes were isolated, classified into the classes Eurotiomycetes, Sordariomycetes, Coleomycetes, and Agariomycetes. Together with other known compounds, five (5) previously undescribed compounds were reported, namely; quinolizidine alkaloids (46-49) and a tirucallane triterpenoid (67), additionally ten (10) phenolic compounds were reported for the first time in this study. The phenolic and quinolizidine alkaloids demonstrated antidermatophytic activity, with minimum inhibitory concentration (MIC) values ranging from 6.6 μg/mL to 300 μg/mL against Trichophyton rubrum, Trichophyton interdigitalle, Trichophyton benhamiae, Microsporum canis, and Nannizia gypsea. The cinnamic acid (65) demonstrated antimicrobial activity against Bacillus subtilis (MIC of 16.6 μg/mL), comparable to oxytetracycline (MIC 16.6 μg/mL). The phenolic compounds also exhibited antiproliferative and cytotoxic effects on KB3.1 and L929 cell lines, with compound 65 demonstrating an IC50 value of 18 μg/mL. The results of this study demonstrate the significance of C. aurea subsp. aurea and endophytic fungi as sources of antimicrobial, antidermatophytic, antiproliferative, and cytotoxic secondary metabolites, which may serve as lead compounds in drug development. Additionally, this study scientifically validates the use of C. aurea subsp. aurea in alternative medicine.